Ultra high frequency tube



Oct. 10, 1950 D. ALPI-:RT

.ULTRA HIGH 'FREQUENCY TUBE Filed March 29, 1943 2 Sheets-Sheet 1 wlT'NEssEs:

2 Sheets-Sheet 2 D; ALPERT ULTRA HIGH FREQUENCY TUBE Oct. l0, 1950 Filed March 29, 1943 A I l l /27 7-9 Patented Oct. 10, 195

ULTRA` HIGHl FREQUENCY TUBE Daniel Alpert, Pittsburgh, Pa., assignor to West'- inghouse Electric Corporation, a corporation of Pennsylvania Application March 29, 1943, Serial No. 480,991

This invention relates to an ultra-high frequency tube and has particular relation to a transmitter-receiver tube for use in ultra-high frequency power systems and apparatus for coupling the tube into the system.

A transmitter-receiver tube, commonly known as a T-R box, is employed in radar systems in which 9, single antenna is used both to transmit and to receive ultra-high frequency signals. The transmitter is connected by wave guides directly to the antenna and the receiver is connected by wave guides to the antenna through the T-R box. The function of the T-R box is to permit lowpower incoming signals to pass to the receiver and to prevent the high-power sign-als from the transmitter from passing to the receiver in sufcient strength to injure the receiver. This function is accomplished by providing a low pressure arc gap Within a highly conducting cavity resonator. High-power signals cause an arc to be established across the arc gap which reflects most of the electromagnetic waves of the signal and prevents their passage to the receiver. However,

when low-power incoming signals are supplied to the T-R box, it acts as a normal cavity resonator and passes the signals to the receiver.

To operate satisfactorily the cavity resonator containing the arc gap must be vacuum-tight' and at a low pressure. There must also be some provision for setting the spacing at the arc gap and for coupling the resonator to the wave guides for eicient transfer of power. Prior T-R boxes of which I am aware are quite complex in structure and employ coupling loops to transfer power between the wave guides and the interior of the T-R box. 'These coupling loops addv greatly to the difficulties in manufacturing and assembling the T-R box. Moreover, the use of coupling loops also necessitates the use of impedance matching and tuning sections, thus adding to the expense as Well as increasing the possibilities of faulty operation.

It is, accordingly, an object of my invention to provide a novel transmitter-receiver tube which is efficient and reliable.

Another object of my invention is to provide a new and improved vacuum-tight cavity resonator.

A further object of my invention is to provide' Still another object of my invention is to pro I vide a vacuum-tight cavity resonator with new 22 claims. (o1. 25o-27.5)

and improved means for coupling the resonator to a wave guide.

More specifically, it is an object of my invention to provide a new transmitter-receiver tube which is simple and inexpensive to manufacture vand assemble and which may be readily coupled in a wave-guide system.

In accordance with my vinvention I provide a T-R box with its interior forming an efficient vacuum tight cavity resonator and its exterior forming parts of hollow transmission line couplings of the choke type with a pair of dielectric windows permitting passage of' electromagnetic waves into and out of the resonator. The box may comprise a body of highly conducting material' having an' internal cavity with two openings to the outside of the body forming inlet and outlet passages for electromagnetic waves. A metallic plate is mounted across each of 'the passages and is secured to the body with a vacuum-tight joint. Each of the plates has an opening therein aligned with the body passage and a dielectric member, preferably glass, of substantially uniform thickness completely fills the plate opening with a vacuum-tight seal' at 'the edge ofthe opening between the plate and the dielectric member.

The T-R box is positioned in the system with an end of a hollow wave guide opposite each of the dielectric members. To couple the T-R box to each of these wave guides, I' propose to mount one section of a hollow transmission line coupling of the choke type on the end of each guide opposite a dielectric member and to shape the exterior of the T-R box surrounding each dielectric member for cooperation with the section mounted on the end' of the wave guide to form a complete coupling of the choke type. A hollow transmission line'c'oup'ling' of the choke type is one which is ordinarily employed'to couple the ends of two hollow wave guides together. It forms an eiii'cient electrical coupling for transmitting electromagnetic radiation without the necessity of a highly enicient mechanical connection. Two plate-like members are usually employed with one mounted' across the end of eachV guide, there being an opening in each plate permitting the free passageof electromagnetic waves from one' guide to the' other; andthe adjacent surfaces of the two plates are shaped to form a quarter wave choke. In other words a space is formed around the gap between the ends of the two Wave guides of such configuration and dimensions as to preventl any substantial loss in 3 though there may be no complete mechanical connection between the two plates.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

Figure 1 is a diagram illustrating the position of the T-R box with respect to other elements in a radar system;

Fig. 2 is a cross-sectional view of the T-R box coupled between two wave guides;

Fig. 3 is a sectional view taken along line III- III of Fig. 2;

Fig. 4 is a sectional view of the T-R box alone, as viewed alongline IV--IV of Fig. 3;

Fig. 5 is an elevational View of the unmounted T-R box;

Fig. 6 illustrates the T-R box with an improved mounting therefor; land Figs. 7 and 8 illustrate the application of the arrangement for coupling the T-R box to a wave guide to the coupling of two'sections of a hollow wave guide which are to be maintained at different pressures.

As shown in Fig. 1, the usual single antenna radar system employs a transmitter II connected by hollow wave guide sections I3 and I5 to the antenna I'I. A receiver I9 is also connected to the antenna II through a hollow wave guide section 2l, a T-R box 23, and wave guide sections 25 and I5. It is apparent that the transmitter I I is also connected tothe receiver I9 and would supply high-power impulses `tending to destroy the receiver during the transmitting period if the T-R box 23 were not present. As previously mentioned, the function of the T-R box is to permit passage of low-power signals from the antenna I'I to the receiver I9 but to attenuate passage of high-power signals from the transmitter II to the receiver I9.

As shown in Figs. 2 through 6, the T-R box 23 includes a disk-like metallic body 21 having al cavity 29 formed therein. One part of the cavity wall is made up of a metal diaphragm 3| which is soldered at its edges to the body 21 with a vacuum-tight joint. The pointed end 33 of a shaft 35 extends through the center of the diaphragm 3| into the cavity 29 and cooperates with a similar pointed member 3'! formed in the body 21 to provide an arc gap. The shaft 35 is soldered to the diaphragm 3l with a vacuum-tight joint, and the opposite end of the shaft is threaded for engagement with the internal threads of a sleeve 39. The exterior of the sleeve 39 is also threaded for engagement with the internal threads of a second sleeve 4I which is flxedly mounted on the body 2'I and held in place by setscrews 43. A cup-shaped cap member 45 covers the ends of the two sleeves 39 and -4I and shaft 35 and is held firmly against a shoulder 41 of the inner sleeve 39 by a washer 49 and screw 5I. Thus, when the cap 45 is rotated, the shaft 35 is gradually adjusted up and down to adjust the length of the arc gap. The lower end of sleeve 39 is slotted as shown at 40 and expanded to maintain the relative positions of sleeves 39 and 4I after adjustment thereof. The exterior of the cap 45 and the second sleeve 4I are calibrated in a manner similar to the calibrations on a micrometer to enable accurate setting of the arc gap.

-inghouse 704 glass.

may be of any desired configuration, but a cir-A 4 thickness.

A make-alive electrode 53 is positioned in a bore 55 provided in the body 2, which bore is connected to the interior of the cavity 29 by a small hole 5l. A tubular member 59 is mounted in the outer end of bore 55, and the make-alive electrode 53 is held in position by a glass Seal yEi between the electrode and the tubular member. The tubular member 59 is preferably formed of an alloy having substantially the same coeicient of expansion as the glass. A direct-current source of power 63 is connected between the make-alive electrode 53 and the body 2l through a hand switch 65. When the switch 55 is closed, a small direct-current arc is established between the end of the make-alive electrode 53 within the bore 55 and the portion of the body 2l adjacent thereto. Since the hole 5l' connects the cavity 29 and bore 55, this arc effects a partial ionization in the space between the main electrodes 33 and 3l to facilitate the striking of the main arc.

The cavity 29 within the body 2l is provided with an opening 61 to each of the flat sides of the body. A recess is machined in the body about each of these openings and a metallic plate 69 is mounted therein, being soldered to the body at 'II with a vacuum-tight joint. Each of the plates 69 has an opening therein aligned with the opening b from the cavity 29 and a dielectric member i3 completely fills the plate opening with a vacuum-tight seal at the edge of the opening between the dielectric member and plate.

The dielectric member I3 filling the opening in each of the plates 69 is preferably glass and must, of course, have substantially the same coeiicient of expansion over the range of temperatures to be encountered as the plate and make a vacuum-tight seal. For thisrreason 1 prefer to form each metal plate 69 of an alloy, which consists chiefly of iron, nickel, and cobalt as described in Patent 2,217,421, issued to Howard Scott on October 8, 1940. With the alloy plate I prefer to use one of the well-known suitable boro-silicate glasses of substantially the same coefficient of expansion as the alloy, such as West- The opening in the plate cular opening is preferred because of the ease of manufacture, the high mechanical strength,Y

and the simplicity of calculations with respect tothe system.

In making a metal supported glass window of a plate 69 and glass member 13, I rst provide an opening of the desired configuration in the metal plate. The edges of the metal at the opening are then rounded and oxidized. A piece of glass which preferably has a conguration which is slightly larger than the opening in the plate, is pressed into the opening while the glass is maintained at such a temperature that it is soft and the edges of the metal plate at the opening are maintained at a temperature such that the oxide partially dissolves in the glass, causing the glass to adhere to the metal. In this manner a vacuum-tight glass-to-metal seal is formed at the edges of the opening.

While the glass in the opening is still soft, molten glass may be added or subtracted therefrom until the glass has a substantially uniform is soft to make use of the effect of gravity, the

surfaces of the glass may be positioned in sub- Y stantially th-e same planes as the corresponding surfaces of the plate. The plate and glass are By turning the plate while the glass i. glass, it may be obtained by-grindingrtheglass after the plate'and glass havecooled.y

The metal supportedglass window manufac` tured in the preferred manner describedhasl ay number of outstanding features:v Asa seal4 is formed simultaneously at all edgesA ofl the open-A ing with the same heat, an exceptionally good! vacuum-tight glass-to-metal seal is provided. InY

addition, the glass and the plate may be made comparatively thin with a substantial-uniform thickness of glass.

supported glass windows of substantially uniform thickness ofthe orderof .G-to .020 inch:-

With such windows electromagnetic waves may pass through the glass with but Very little loss and'very little distortion or interference.

I- have also found that the metal supportedl glass window is extremely strong mechanically. Not only may the glass be ground after the sealA is formed, but the plate may also be'machined without breaking the glass or destroying the vacuum-tight seal. I have discovered thatA the plate may be soft-soldered to other apparatus at any point up to the edge of the glass, and that it may be hard-soldered or spot-welded'to other apparatus as close as of an inch from the edge of the glass. Further details with respect to the manufacture and properties of such a metalsupported glass window may be found in my copending application Serial No. 480,990, filed March 29, 1943, now United States Patent No. 2,419,049, issued April 15, 194'7.

In assembling the T-R box 23, the diaphragm 3| is first soldered to the shaft 35, and then with the shaft 35 and diaphragm 3| in position, the diaphragm is soldered to the body 21. The two metal supported windows are positioned on the body and soldered in -plaoe while hydrogen is passed through the body to keep the interior` thereof clean by way of two auxiliary passages having sleeves 'Il soldered in the outer ends thereof. After the windows are secured in place the interior of the T-R box is evacuated and the sleeves 11 are closed off.

As shown in Figs. 1 and 2, the T-R box 23 is to be mounted between two hollow wave guides 2| and 25. The wave guides may have either a circular or rectangular cross-section or any other cross-section which may be desired. The end of one Wave guide 2| is positioned opposite one glass member '13 in the T-R box, and the end of the other wave guide is positioned opposite they other glass member 13. On the end of each of the wave guides 2l and 25 is mounted one section 19 of a hollow transmission line coupling of the chok-e type. The exterior of the T-R box surrounding each glass member 'I3 is then shaped as a second section of a coupling for cooperation with the section on the end of the wave guide to form a complete coupling of the choke type.

The section i9 of the coupling mountedv on the end of each of the wave guides 2| and 25 is a metallic plate-like member having an annular slot 8| therein parallel to the axis of the correspending wave guide. The exterior of the T-R box 23 surrounding each glass member 13 including a portion of the body 2l and the corresponding metal plate 59 is shaped to provide a at surface adjacent the coupling section mounted on the wave guide. The surface of the coupling section 'i9 bounded by the annular slot 8 |r is cut away slightly to provide a space betweenV it andthe adjacent surface of the T-R'.A box. The portion of each couplingsection '|9- outside of In preparing T-R. boxes cfthe type disclosed herein, I havel prepared metal of the tube.

slot-8| then abuts against the '"R box; and the. TR box and coupling sections are releasably in terconnected -by bolts 83.

'When electromagnetic Waves travelling along one of the guides 2| or 25 come tothe discontinuity at the gap betweenA the end of the guide and exterior wall of the T-R box, some of the waves tend to travel outwardly toward the circumference of the choke. However, the-slot 8| isone-quarter of a wave length deep so that the low impedance at the bottom en-d of the slot 8| causes a high impedance atY the end of the slot adjacent; the T-R box. The slot '8| is located at such a distance froml the guide that the electromagnetic waves traveling toward the circumference are reilected at the end of the slot adjacent the T-R. box and the waves in the guide pass the gapwithout substantial loss in power even though the mechanical connection between the coupling sectionand the box is incomplete.

In Fig. 6 another method of releasably interconnecting the coupling sections 19 and the T-R box 23 is illustrated. An insulating socket 85 is secured to both of the coupling sections 19 and .i maintains them in a properly spaced position.

One ror more prongs 81 are mounted on the out- Side of the T-R box 23 for cooperation with holes in the socket 85 to support the T-R box in position betweenthe coupling sections. With either of the arrangements of Figs. 2 andY 6, the T-R box may be quickly removed from the system for inspection or replacement. rangement of Fig. 6 is particularly advantageous in that the T-R box may be removed more quickly andthe coupling sections are maintained in their proper spaced relationship.

vItis to be noted that while each metal plate 59 supporting a glass member 'i3 is illustrated as being of a comparatively small diameter, it may be of a much larger diameter, if desired, and may of itself form the entire section of the coupling on the exterior of the T-R box. It is believed to. be preferable to keep the metal plate of a small diameter, however, because such an arrangement enables greater use of a material having ahigher conductivity in the constructionof the T-R box, resulting in a more efficient tube. The plate may also loe-used. to form a part of the cavity wall although a material of higher conductivity is preferable for a cavity wall.

It` is also to be noted that the use of a metal supported glass window of the type described is extremely advantageous in this application. A direct transfer of ultrafhigh frequency power be- Atween the guide and cavity resonator. is permitted, without the use. of coupling loops. When the glass is within the opening in the metal plate as illustrated, it can bemade quite .thin and. of uniform thickness with an extremely good vacuum-tight seal. If the glass wereplaced within the resonant cavity, the electrical losses in the resonator would be considerably increased, and the presence of the glass would eiect a mechanical construction greatly limiting the tuning range If the glasswere placed outside of the cavity, considerable mechanical difficulty` would be encountered in coupling the tube tothe wave guide, and there is likelihood of a gas discharge in the waveguide. An attempt to make the glass seal within a regular wave guide passageway results in a glass window which is comparatively-'thick andl which in addition varies widely in thickness sothat power losses are high and the electromagnetic wavesare distorted. VIn addition the Wave guide passageway mustv have a;

However, the ar' tothe passage of electromagnetic waves there through, a greater proportion of the entire wall of the cavity within the T-R, box may be of conducting material when the metal supported glass window of the type described is employed. Thus, the efficiency of the cavity resonator may be maintained at a high level. v

The use of the special metal supportedglass window to form ajsection of a coupling of the choke type between two components of a hollow transmission line which are maintained at different pressures is discussed hereinbefore with reference to the coupling of a T-R box or other tube to a wave guide. However such a coupling may also be employed in -coupling other components such as two wave guides which are to be maintained at different pressures, as illustrated in Fig. '7. Here the metal supported glass window comprising a metal plate 89 having a central opening therethrough filled with glass having a vacuum-tight glass-to-metal seal at the edges of the opening, is mounted ,across the end of one wave guide 9i and secured thereto with a vacuum-tight joint. Another plate-like member 93 having an opening therethrough fitting over the end of the second wave guide 95, is mounted crosswise of the second guide. The two guides are4 positioned coaxially, with a surface of the plate 89 and a surface of the plate-like member 93 adjacent to each other. The surface of the platelike member 93 is shaped in a manner similar to the coupling section 'i9 in Fig. 2 and cooperates with the adjacent surface of the plate 89 to form a complete coupling of the choke type. The two coupling members may be held in position by bolts 96. is of course, the same as that of the choke coupling in Fig. 2.

If it is not necessary or desirable to permit separation of two wave guides which are to be maintained at different pressures, an arrangement as illustrated in Fig. 8 may be employed. A metal plate 91 having a central opening filled by a glass member 99 with a Vacuum tight glassto-metal seal is inserted cross-wise between the ends of two wave guides IBI and |03 and soldered thereto with Vacuum-tight joints. The arrangement shown is possible because the wave guide ends may be soldered to the plate 91 at a point closely adjacent to the glass 99 withoutbreaking the glass or disturbing the seal. It is true that whenever there is a sharp discontinuity in the dimensions of a wave guide a large reflection of electromagnetic radiation may occur. However, inasmuch as the presence of a dielectric, such as glass within a metal opening, permits passage of a greater amount of electromagnetic radiation therethrough, the window size in the arrangement, as shown in Fig. 8, may be made the same in effect as the vsize ofV the wave guide itself although the guide is secured to the metal plate supporting the glass. In this manner reflection of radiation is eliminated.

Although Ihave shown and described certain specific embodiments of my invention, I am fully aware that many modifications thereof are possible using the principles herein disclosed. My invention, therefore, is not intended to be restricted to the specic embodiments shown and described.

The effect of the choke coupling of Fig. 7

,I1 'claim asjmy invention:-v

1. An ultra-high-frequency tubeY comprising a hollow metallic member having an opening from the interior to theoutside thereof, a substantially flat 4metallic platemounted across said opening and Secured to saidv member with a vacuum-tight joint, saidr plate having an opening therethrough aligned with said first-mentioned opening, and a dielectric member within said plate opening with avvacuumV-tight seal at the edge of said plate opening between said dielectric member and plate,V said dielectric Vmember having substantially the same Vcoefficient of expansion assaid plate and being locatedwithin the boundaries formed by the planes of the surfaces of said plate.

2. An ultra-high-frequency tube comprising a hollow metallic member having an opening from the interior to the outside thereof, a substantially fiat metallic' plate mounted across said opening and Ysecured to said member with a Vacuum-tight joint, said plate having an opening therethrough aligned with said first-mentioned opening, and a dielectric `member within said plate opening with a vacuum-tight seal at the edge of rsaid plate opening between said dielectric member and plate, said dielectric member having substantially the same coemcient of expansion and thickness as said plate with each surface of said dielectric member in the same plane as the corresponding surface of the plate. 1

3. Apparatus comprising a hollow metallic body having two separate passageways foi electromagnetic waves between the inside and outside thereof, a rst hollow wave guide .positioned with an end adjacent to and aligned with the outside end of one of said passageways, said first guide having a member on said end thereof with a metallic surface adjacent the exterior surface of Ysaid body surrounding said one passageway, a second hollow wave guide .posi` tioned with an end adjacent to and aligned with the outside end of the other of said passageways, said second guide having a member on said end thereof with a metallic surfaceadjacent the exterior surface of said body surrounding said other passageway, the adjacent surfaces of said member and body corresponding to each of said guides forming a choke for the electromagnetic waves, and means releasably interconnecting said body and said first and second guides for maintaining them in position.

4. Apparatus comprising a hollow metallic body havingtwo separate passageways for electromagnetic waves between the inside and outside thereof, a first hollow wave guide positioned with an end adjacent to and aligned with the outside end of one of-said passageways, said first guide having a member on said end thereof with a metallic surface adjacent the exterior surface of. said body surrounding Asaid one passageway, a secondhollow wave guide positioned with an end adjacent to and aligned with the outside end of the other of said passageways, said second guide having a member on said end thereof with a metallic surface adjacent the exterior surface of saidV body surrounding said other passageway, the adjacent surfaces of said member and body corresponding to each of said guides forming a choke for the electromagnetic waves, said body having at least one projection on the outside thereof, and an insulating socket base interconnecting said first and second guides and having an opening therein into which said projection extends whereby said body is removably supported between said first and second guides,-

5. Apparatus comprising a tube including a hollow body having a vacuum-tight internal cavity with a wall portion through which electromagnetic waves may pass between the inside and outside of said body, and a hollow wave guide having an end positioned adjacent said portion and aligned therewith, said guide having a member on said end thereof with a metallic surface adjacent the exterior surface of said body surrounding said portion, the adjacent surfaces of said member and body forming a choke for the electromagnetic waves.

6. An electromagnetic wave system comprising a hollow body having an opening between the inside and outside thereof, a substantially flat metallic plate mounted across said opening and secured to the exterior of said body, said plate having an opening therethrough aligned with said first-mentioned opening and a dielectric member within said plate opening sealed to said plate at the edge thereof, said dielectric member having substantially the same coefficient of expansion and .thickness as said plate with each surface of said dielectric member vin substantially the same plane as the corresponding surface of the plate, whereby is provided a -passageway for electromagnetic waves between the inside and outside of said body through said rst-mentionedopening and said dielectric member, a hollow wave guide havingan end positioned adjacent said dielectricimember and aligned with said passageway, said guide having a flange-like member on an end thereof with an outwardly extending metallic surface adjacent the exterior surface of said body surrounding said passageway, the adjacent surfaces of said body and iiange-like member forming a choke for the electromagnetic waves, and means releasably inter'- connecting said bodyvand guide for maintaining them in position.

'7. Apparatus comprising a hollow body having a vacuum-tight internal cavity with a wallr` portion through which electromagnetic waves may pass between the inside and outside of said body, a hollow wave guide havingan end positioned adjacent lsaid portionv and aligned therewith, said guide having a member on said end thereof with a metallic surface adjacent the exterior surfacevof said body surrounding said portion, the

adjacent surfaces of said member andl body forming a choke for the electromagnetic waves, and means releasably rinterconnecting saidy body and guide for Amaintaining them in position. v 8. Apparatus com-prising Ia hollow, disk-like, metallic body having two passageways for electromagnetic waves extending between the inside and outside of said body on opposite sides thereof, a first Ahollow wave guide having anend lpositioned adjacent to and aligned with the first of said passageways, a second` hollow wave `guide having an end positioned adjacent to and aligned with the second of said passageways, each of said guidesk having a member on said end thereof with an outwardly extending metallic surface. adjacent to the side surface `of said body surrounding the corresponding passageway, the adjacent surfaces ofieach member and the corresponding body side forming a choke for the electromagnetic waves. i l

9. Apparatus comprising a hollow, disk-like metallic body having two passageways for ,electromagnetic waves extending between the inside and `outside of said member on opposite sides thereof, a first hollow vwaveguide Vhaving anend positioned adjacent to `land aligned with the first 10 of said passageways, a second hollow wave guide having an end positioned adjacent to and aligned with the second of said passageways, each of said guides having a member on said end thereof with an outwardly extending metallic surface adjacent to the side surface of said body surrounding the corresponding passageway, the adjacent surfaces of each member and the corresponding body side forming a choke for the electromagnetic waves, and means releasably interconnecting said body and guides for maintaining them in position.

10. An electromagnetic wave system comprising a hollow body having an opening between the inside and outside thereof, ametallic plate mounted across said'o'pening and secured to said body with a vacuum-tight joint, said plate having an opening therethrough aligned with said iirst-mentioned opening and a dielectric member within said plate opening with a vacuum-tight seal at the edge of said plate opening between said dielectric member and plate, whereby is provided .a passageway for electromagnetic waves between the inside and outside of said yhollow body including said first-mentioned ,opening and ,said dielectric member, a hollow Wave guide having an end positioned adjacent said dielectric member and aligned with said passageway, said guide having a iiange-like member on said end thereof with a metallic surface adjacent the exterior surface of said body surrounding said passageway, the adjacent surfaces of ysaid bodyand flange-like member forming a choke for the electromagnetic waves, and means releasably interconnecting said hody and guide for maintaining ,them in positionf 11. An electromagnetic wave system comprising a hollow body havingan openingbetweenthe inside and outside thereof, a metallic plate mounted across said opening and secured to said body with a vacuum-tight joint, .said plate ,having an opening therethrough aligned withsaid first-mentioned vopening and a dielectric member within said ,plate l,opening with a vacuumtightseal at the edge of said plate opening betweenV said dielectric member and plate, said dielectric V., member "being of substantially uniform thickness andhaving substantially the same coefficient of expansion as said plate, a hollow wave guide having an end positioned adjacent said dielectric vmember'andaligned with said passagewaysaid guide having a flange-like member on said end thereof withk a metallic surface adjacent the exterior surface of said body surrounding said passagewlay,v the ,adjacent surfaces of said body and flange-like member forming a choke for the electromagnetic waves, and means releasably interconnecting said body and guide for maintaining them in position.

12. Apparatus comprising adisk-like body including a hollow disk-like metallic member having twoopenings extending from ,the inside to thecutside of said member on opposite sides thereof, a metallic plate mounted Aacross each of said openings'and secured to said member with a `vaenum-tight joint, ,each of said plates having an aperture therethrpugh aligned with `the corresponding opening, anda dielectriemember within each of said apertures with a vacuum-tight seal at ,the yedge thereof between the dielectric memberand plateeah ef ,Seid dielectric plate, ,each of said dielectric members having a substantially uniform thickness and substantially the same Vcoeflicie'nt .of expansion as the correv sxpkondinglplate, Awhereby provided a Ypassageway 11 for electromagnetic waves between the inside and outside of said disk-like body on opposite sides thereof through the corresponding opening and dielectric member, a first hollow wave guide having an end positioned adjacent one side of said body and aligned with the corresponding passageway, a second hollow wave guide having an end positioned adjacent the other side of said body and aligned with the corresponding passageway,

, each of said guides havinga flange-like member on an end thereof with a metallic surface ,adjacent the side surface of said body surrounding the corresponding passageway, the adjacent surfaces of each flange-like member and said body forming a choke for the electromagnetic waves, and means releasably interconnecting said body and guides for maintaining them in position.

13. Apparatus comprising a hollow guide for electromagnetic waves, a metallic plate positioned across said guide with an opening therein aligned with the bore of the guide, and a dielectric member wholly within the boundary of said opening with a vacuum tight seal at the edge thereof between the dielectric member and said plate, said dielectric member being substantially uniform in thickness and having substantially the same coelicient of expansion and thickness as said plate.

14. Apparatus comprisingxa hollow guide for electromagnetic waves andga wall' extending across the bore of saidguide including a window of a material transparent to the electromagnetic waves aligned with said bore and permitting transmission of the waves from the guide through said window without substantial reflection with the whole peripheral surface of said window falling everywhere within the Voutline of said open- 15. Apparatus comprising a -hollow guide -for electromagnetic waves-a, metallic wall extending across. the bore of. said guide having an openingtherethrough aligned with said bore,.l and a dielectric member within said opening-,sealed to said wall at the edge of the opening, saiddielectric member permitting transmission of. electromagnetic waves from the guide through said dielectric member without substantial reflection with the whole peripheral surface of said dielectric member falling everywhere within Athe., outline of said opening.

16. A cavity resonator for use in an electromagnetic wave system, said cavity resonator cornprising hollow wave guide to which theresonator is to be coupled, said guide having a flange at an end thereof extending radially outward from the guide at substantially right angles to the axis thereof, a hollow body ,of conductive material having a passageway forelectromagnetic waves between the inside and outside thereof and mounted with the outer end of the passageway in axial alignment with said guide, the exterior surface of the body surrounding the passageway extending radially therefrom at substantially right angles to the axis thereof for a distance greater than the radial distance from the axis to the walls .of the guide said extending exterior surface being spaced from the surface of said flange so that a choke may be formed between the adjacent surfaces of said body and flange.

l1'7. Afcavity resonator for use in an electromagnetic wave system, Vsaid cavity resonator comprising pair of axiallyaligned hollow wave guides to which the resonator is to be coupled, the adjacent ends of said guides being spaced Y apart with each said end having a ange thereon extending radially outward from the guide at sub.,

stantially right angles to the axis thereof, a hollow, disk-like, metallic body having two axially aligned passageways for electromagnetic waves between the inside and outside of the body on opposite sides thereof, said body being mounted between said ends with the passageways aligned with said guides, the exterior surface of the body surrounding each passageway extending radially therefrom at substantially right angles to the axis thereof for a distance greater than the radial distance lfrom the axis of the guide to the walls thereof said extending exterior surface being spaced from the surface of said flange so that chokes may be formed between adjacent surfaces of said body and flanges.

18. A cavity resonator for use in an electromagnetic wave system, said cavity resonator comprising hollow wave guide to which the resonator is to be coupled, said guide having a flange at an end thereof extending radially outward from the guide at substantially right angles to the axis thereof, a hollow body including a hollow member of conductive material having a passageway for electromagnetic waves between the inside and outside thereof Vand mounted with the outer end of the passageway in axial alignment with said guide, a metallic plate secured to said member across said outer `end and having an opening therethrough aligned with said passageway and a dielectric member withinsaid opening sealed to the platey at the 'edge thereof, the exterior surface of the body surrounding the passageway extending radially therefrom at substantially right angles vto the axis thereof for a distance greater than vtheradial distance from the axis to the walls of the guide whereby a choke may be formed between the adjacent surfaces of said body and ange.

19. Apparatus comprising a hollow guide for, f

electromagnetic waves a metallic wallextending across the bore of said guide having Aan opening therethrough aligned with saidbore, said wall being of an alloy containing chiey iron, nickel and cobalt, and a boro-silicate glass member of substantially the same Acoeflicient of .expansion as vout substantial reflection with the whole peripheral surface of said glassmember falling everywhere within the outline of said opening.

20. A cavity resonator .foruse in an electromagnetic wave system with a hollow wave guide to which the resonatoris to be coupled. said guide having a ange at an endA thereof extending radially outwardfrom the guide at substantially right angles to the axis thereof, said cavity resonator comprising Va hollow bodyof conductive material having a passageway for electromagnetic waves between the inside and the outside thereof, the exterior surface Vof the body surrounding the passageway extending radially therefrom at substantially right angles to the axis thereof for adistance greater than the radial distance from the axis tol thewalls of the guide, said extending exterior, surface beingV -spaced from the surface of said flange so that a choke may be formed between `theadjacent surfaces ofV said body and flange, vand whereby the passageway may be positioned in axial alignment with said guide. n

21. A cavity resonator for use in an electromagnetic wavel system with a pair of axially aligned hollow wave guides to which the resonator is to be coupled, the adjacent ends of said guides being spaced apart with each said end having a flange thereon extending radially outward from the guide at substantially right angles to the axis thereof, said cavity resonator comprising a hollow disc-like metal body having two axially aligned passageways for electromagnetic waves between the inside and outside of the body on opposite sides thereof, the exterior surface of the body surrounding each passageway extending radially therefrom at substantially right angles to the axis thereof for a distance greater than the radial distance from the axis of the guide to the walls thereof, said extending exterior surface being spaced from the surface of said flange so that chokes may be formed between adjacent surfaces of said body and flanges, and whereby the passageway may be positioned in axial alignment with said guide.

22. A cavity resonator for use in an electromagnetic wave system with a hollow wave guide to which the resonator is to be coupled, said guide having a flange vat an end thereof extending radially outward from the guide at substantially right angles to the axis thereof, said cavity resonator comprising a hollow body including a hollow member of conductive material having a passageway for electromagnetic waves between the inside and outside thereof, a metallic plate secured to said member across said outer end and having an opening therethrough aligned with said passageway and a dielectric member within said opening sealed to the plate at the edge thereof,

the exterior surface of the body surrounding the passageway extending radially therefrom at substantially right angles tothe axis thereof for a distance greater than the radial distance from the axis to the walls of the guide, said extending exterior surface being spaced from the surface of said flange so that a choke may be formed between the adjacent surfaces of said 'body and flange, and whereby the passageway may be positioned in axial alignment with said guide.

DANIEL ALPERT.

REFERENCES CITED The following referencesr are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,128,234 Dallenbach Aug. 30, 1938 2,200,023 Dallenbach May 7, 1940 2,216,169 George et al Oct. 1, 1940 2,217,421 Scott Oct. 8, 1940 2,231,274 Dallenbach Apr. 28, 1942 2,341,920 Hull Feb. 15, 1944 2,372,193 Fisk Mar. 27, 1945 2,403,303 Richmond July 2, 1946 2,404,226 Gurewitsch July 16, 1946 2,419,049 Alpert Apr. 15, 1947 2,467,730 Coltman Apr. 19, 1949 FOREGN PATENTS Number Country Date 4,47 9 Great Britain Feb. 27, 1908 

